I've always loved retro games, especially on the programming side. One thing that always fascinated me was the use of palettes. It was a simple tool, but it was used to great effect. I wanted to create a tool that used that, and create it I did. This tool has a lot of flexibility, while also running with minimal impact to the performance. It has support for many things:

Sprites of any size and shape (no limitation to a 8x8 or 16x16 grid size)

Global palette system, allowing the switching of one palette to affect multiple sprites at once

Palettes are easily modified, both in editor and while the game is running

Two ways of rendering sprites:

Each sprite rendering to a separate Sprite Renderer component, allowing for full rotation and scaling

One "camera" like object, taking sprite data and rendering sprites to the main sprite

Has support for Unity's tileset editor (not yet uploaded to the asset store)